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Biochemistry
Chloride is the most abundant negatively charged electrolyte in your blood, working alongside sodium and bicarbonate to hold your body's fluid balance and acid-base status steady. This test is almost never ordered by itself; it's one line on a broader electrolyte panel or metabolic panel, read together with sodium, potassium, and bicarbonate rather than in isolation, because chloride moving on its own, without the others, rarely tells a complete story. It tends to rise with dehydration or a build-up of acid in the blood, and tends to fall with vomiting, since stomach acid is chloride-rich and repeated vomiting can strip a meaningful amount of it from the body.
The test reports chloride concentration in blood, in milliequivalents per litre; a typical reference range runs from about 98 to 107 mEq/L, though exact ranges vary by lab. It's reported alongside sodium, potassium, and bicarbonate as part of the same electrolyte or metabolic panel, since chloride's movement relative to bicarbonate specifically, the two tend to shift in opposite directions, is often more informative for reading acid-base status than the chloride figure alone.
Chloride's main job is maintaining the electrical and fluid balance across your body's cells and blood vessels, working as a counterweight to sodium and to bicarbonate. Because of that shared role, chloride is essentially never read alone; it's one part of a small group of electrolytes whose relative movement, not any single number, carries clinical meaning.
Dehydration concentrates everything in the blood, chloride included, so a raised level is common with significant fluid loss. Metabolic acidosis, a build-up of acid in the blood from causes including kidney disease and severe diarrhoea, also tends to raise chloride as the body's buffering systems shift.
Repeated vomiting is one of the more direct causes of low chloride, since stomach acid is rich in chloride and heavy losses through vomiting can meaningfully deplete the body's supply, tipping the blood toward the opposite acid-base state, metabolic alkalosis. Heart failure and some lung diseases have also been linked to lower chloride readings, generally through their effects on the body's broader fluid balance rather than through any direct loss of chloride itself.
Because several unrelated conditions can move chloride in the same direction, an abnormal result is read together with the other electrolytes on the same panel, and with the clinical picture, before it's linked to a specific cause.
It's read alongside sodium, potassium, and bicarbonate on the same panel, since its movement relative to the others carries more meaning than the chloride number by itself.
Repeated vomiting is one of the more direct causes, since stomach acid is chloride-rich. Heart failure and some lung diseases have also been linked to lower readings.
Yes. Losing stomach acid through repeated vomiting can meaningfully deplete the body's chloride, tipping the blood toward metabolic alkalosis.
It's often linked to dehydration or metabolic acidosis, a build-up of acid in the blood, though it's interpreted alongside the other electrolytes on the same panel.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
No. They're both electrolytes measured on the same panel, but chloride carries a negative charge and sodium a positive one, and they're read together rather than interchangeably.
Chloride and bicarbonate tend to shift in opposite directions as the body adjusts its acid-base balance, which is why comparing the two is often more useful than looking at chloride alone.